Rectifying system



April 9, 1929. AQKI 1,708,751

RECTIFYING SYSTEM Filed April 25, 1927 Inventor: Saber Aoki, by

His Atmornen Patented Apr. 9, 1929.

UNITED STATES PATENT OFFEQZE.

SATABO AOKI, OF EBARA, TOKYO, JAPAN, ASSIGNOB TO GENERAL ELECTRIC COM-PANY, CORPORATION OF NEW YORK.'

RECTIFYING SYSTEM.

Application filed April 25, 1927, Serial No. 186,201, and in Japan June23. 1926.

My invention relates to rectifying systems wherein power is transmittedbetween direct and alternating current circuits through means comprisingmain and interphase transformers, and has for its principal object theprovision of an improved transformer which may be utilized in suchsystems to perform the functions heretofore performed by both the'main,transformer and the interphase transformer.

It is well known that in the operation of a recitifier comprising acathode and a plurality of anodes, each connected to a, different phaseof an alternating current circuit, current is successively carried byeach of the anodes during a period of time dependent on the number ofphases and the frequency at which power is delivered to the rectifier.It is customary to connect such a rectifier to the alternating currentcircuit through a main transformer provided with two three-phasesecondary windings which have their neutral terminals interconnectedthrough an absorption coil or interphase transformer and are arranged toproduce three-phase voltages 180 out of phase with one another. \Viththese connections, the voltage difference between the phasessimultaneously transmitting current is absorbed in the interphasetransformer and the voltages of the anodes simultaneously transmittingcurrent are maintained substantially equal. In accordance with myinvention, the same result is produced by means comprising an additionalleg on the core of the main transformer.

My invention will be better understood from the following descriptionwhen considered in connection with the accompanying drawings, and itsscope will be pointed out in the appended claims.

Referring to the drawings, Figs. 1 and 2 diagrammatically showrectifying systems wherein my invention has been embodied; and Figs. 3and 4 relate to the operation of these systems.

Fig. 1 shows alternating current terminals 1 and direct currentterminals 2 which are interconnected through means comprising arectifier 3 and a polyphase transformer provided with a star-connectedprimary winding 4, with an absorption coil or interphase transformerwinding 7, and with a pair of star-connected secondary windings 5 and 6arranged to produce polyphase voltages which are 180 out of phase withone another. .The windings 4, 5 and 6 are wound on the legs 8 of thetransformer core in the usual manner. The coil 7 is wound on a leg 9 ofthe transformer, is connected between the neutral terminals of thewindings 5 and 6, and is provided with an intermediate terminal which isconnected to one ofthe direct current terminals 2. \Vith theseconnections, the primary winding at and the interphase transformerwinding 7 tend to produce in the cores 8 and 9 fluxes which have triplethe frequency of the power delivered at the terminals 1 and react uponthe secondary windings 5 and 6 in a manner to maintain substantialequality between the voltages of the anodes simultaneously transmitting.

The manner in which this result is accomplished will be readilyunderstood upon reference to Figs. 3 and 4 wherein the voltages thatwould be induced in the windings 5 and 6 in the absence of the triplefrequency flux are indicated by the numerals 5,, 5. 5 6,, 6 and 6,, thevoltages produced in the windings 5 and 6 by the triple frequency fluxare respectively indicated by the curves 10 and 11, and the resultantvoltages produced in the windings 5 and 6 and applied to the anodes ofthe rectifier are indicated by 5 5 5 6 6 and 6,. It will be observedthat the voltage 6 is the resultant of the voltages 6,. and 10; that thevoltage 5,, is the resultant of the voltages 5 and 11; that the voltage6 is the resultant of the voltages 6 and 10; that the voltage 5 is theresultant of the voltages 5 and 11; that 6 is the resultant of thevoltages 6 and 10; and that the voltage is the resultant of the voltages5 and 11. With these resultant voltages each applied to a ditferentanode of the rectifier, current will be transferred from one anode toanother at the instants t, 23,, t. t t t and t and current will betransmitted through different pairs of the anodes during the timeintervals zf-t,, t,t. t. .t, t,t t t and t,,t due to the fact that thevoltages of these pairs are substantially equal during the indicatedintervals. Thus, the resultant anode voltages 6, and 5 are substantiallyequal during the interval t-t,, the anode voltages 5 and 6 aresubstantially equal during the interval f,t the anode voltages 6 and 5are substantially equal during the interval t t the anode voltlit)interval z ,z r, and the anode voltages 5, and,

(i, are substantially equal during the interval 12-1,,

It should he noted that the trrfrp-le -fne quency voltage 10 of thewinding (3 and the triple frequency voltage 11' ot the winding 5 areproduced by the same triple frequency flux and are 180 out of phase withone another because the windings-5 and 6 [1T8 arranged to produceopposed voltages. Since :this trirple frequency flux is transmittedthrough all the core legs simultaneously, its effect on the terminalvoltage of t he' winding l-is nil. "The fact that a part of the triplefrequency voltages required to 'bailance'the voltages of the anodessimultaneously transmitrting current is produced by the primary winding4 makes it possible to'reduce the size of the interphase transformerwinding 7. As indicated by Fig. 2, this winding may be altogetheroii'iitted. One way of producing tlie 'triple frequency flux in theabsence the interphase transformer is to so arrange the windings andcoreaof the transformer that rthe core is operatedat or near saturation.it will be understood that this flux may also be produced other ways.\Vhile I have described my invention as applied to atransf-omnerprovided with a secondary circuit connected in star, it willbe apparent that its advantages are not limited to this particular typeof connection.

The embodiments of the invention illus- (rated and described hereinhavebeen sseleeted for the purpose otclearly setting torth theprinciples involved. It will he appnrout, however, that the invention issusceptible of being, modified to meet the different conditionsencountered in its use, and I, therefore, aim to cover by the appendedclaims all modifications 'within, the true sprrrt and scope of myITI'VGDUOIL lVhat I claim as new, and desire to secure by Letters.Patent-of the United States, is:

l. The combination of a transformer including a multi-leg core,polyphase windings wvound only on some of said legs and pro 1inter-phase winding, 7

2. Infasystem-for interconnecting direct and a'lterna'ting'eurrentcircuits, the 'combinationof a'multi leg core, polyphase windingswound"onily on some of said legs and provided with end. and neutralterminals,

and an interplrase :windin; mvound on the btlher of said legs andconnected-between said aieirtral' teiiminals. v

In a 'system 'for interconnectingthreephase and direct cnrrentcircuits,the comlfmation ot-1a core prowided-with four legs, polyiplms'e'windimgs wound :on t-hreeof said legs and provided with. end andmeutral terminals, and an interphasewinding wound on the othemof saidalegs and connected between said'neutra'l terminals. 1- a 4. In a system1 for interconnecting threephase and direct current circuits, thecomebinationof :a eoreprovided with fourxlegs, ;tw'vo -Y-connectedwlndings wound onthree of said legs,.-and an Einterphase winding woundon "the other of sa-id legs and conncotedbetween the neutral terminalsof said sA'r Ro AOKI.

